Single-use encapsulated hot pack activator

Abstract

An activator (10) made in accordance with the principles of the present invention includes activating crystals (11) that have been formed into a shape and then coated with coating (12). The activator (10) of the present invention can be used in any environment in which the solidification of a supercooled solution occurs and whereby heat is generated during the solidification process. In the preferred embodiment disclosed herein, the activator is placed inside a hot pack (15) containing a supercooled solution (16). The hot pack can be made of a container made of a thermoplastic film which is formed into a bag, filled with activator (10) and the supercooled solution (16), and sealed to form the hot pack. The coating (12) of the activator (10) is impervious to the supercooled solution (16) in the hot pack (15) and into which the activator will be placed. The supercooled solution (16) may be any of a variety of chemical compositions known in the art which give off heat as they solidify.

I claim: 
     
       1. An activator for initiating solidification of a supercooled salt solution, the activator comprising: a shaped solid comprising a plurality of salt crystals, the shaped solid being fracturable by hand to produce at least two pieces; and a coating completely covering the shaped solid, the coating being impervious to a supercooled salt solution in which the activator may be placed and fracturing upon fracturing the shaped solid, the coating being selected from the group consisting of: synthetic rubber and wax.   
     
     
       2. The activator of claim 1, wherein the shaped solid is scored. 
     
     
       3. The activator of claim 1, wherein the shaped solid has a shape selected from the group consisting of cylinder, ovoid, sphere, parallelepiped, pyramid, cone, and polyhedron. 
     
     
       4. The activator of claim 1, wherein the coating is poly(methyl methacrylate-co-ethyl acrylate), poly(methyl methacrylate-co-vinyl acetate), or a mixture of poly(methyl methacrylate-co-ethyl acrylate) and poly(methyl methacrylate-co-vinyl acetate). 
     
     
       5. The activator of claim 1, wherein the coating is a synthetic rubber. 
     
     
       6. The activator of claim 1, wherein the coating is a wax selected from the group consisting of paraffin wax, bees wax, branched-chain hydrocarbons, a mixture of esters of higher fatty acids, higher fatty alcohols, free higher acids, free higher alcohols and saturated hydrocarbons, and mixtures of any of the foregoing. 
     
     
       7. The activator of claim 1, wherein the plurality of salt crystals include a salt crystal selected from the group consisting of sodium thiosulfate pentahydrate, sodium tetaborate decahydrate, sodium acetate trihydrate, a eutectic combination of sodium thiosulfate pentahydrate and sodium acetate trihydrate, and mixtures of any of the foregoing. 
     
     
       8. The activator of claim 1, wherein the plurality of salt crystals comprises a mixture of salt crystals having at last two different chemical formulas. 
     
     
       9. The activator of claim 1, wherein the plurality of salt crystals includes at least one salt crystal having a chemical formula which is the same as a salt used to make a supercooled salt solution to be solidified using the activator. 
     
     
       10. The activator of claim 1, wherein the plurality of salt crystals includes at least one salt crystal having a unit cell dimension which is within about 15% of a unit cell dimension for a salt crystal used to make a supercooled salt solution to be solidified using the activator. 
     
     
       11. The activator of claim 1, wherein the plurality of salt crystals comprise from about 95% to about 100% of a first salt and from about 5% to about 0% of a second salt. 
     
     
       12. An activator for initiating solidification of a supercooled salt solution, the activator comprising: a shaped solid comprising from about 95 percent to about 99 percent by weight, based on a total weight of salt crystals, of sodium thiosulfate pentahydrate and from about 1 percent to about 5 percent by weight, based on the total weight of the salt crystals, of sodium tetraborate decahydrate, the shaped solid being fracturable by hand to produce at least two pieces; and   a coating completely covering tie shaped solid, the coating being impervious to a supercooled salt solution in which the activator may be placed and fracturing upon fracturing the shaped solid, the coating being selected from the group consisting of: synthetic rubber and wax.   
     
     
       13. The activator of claim 12 wherein a sum of the percent of the sodium thiosulfate pentahydrate and the percent of the sodium tetraborate decahydrate is 100 percent. 
     
     
       14. The activator of claim 12 wherein the shaped solid is an ovoid. 
     
     
       15. The activator of claim 14 wherein the width of the ovoid is from about 0.25 inch to about 0.75 inch, the length is from about 0.5 inch to about 2.0 inches, and the thickness is from about 0.05 inch to about 0.5 inch. 
     
     
       16. The activator of claim 12 wherein the shaped solid is a cylinder. 
     
     
       17. The activator of claim 16 wherein the cylinder is from about 0.5 inch to about 2.0 inches in diameter and from about 0.05 inch to about 0.5 inch in thickness. 
     
     
       18. The activator of claim 12 wherein the shaped solid is scored to facilitate fracturing the shaped solid into two or more pieces. 
     
     
       19. The activator of claim 12 wherein the coating is poly(methyl methacrylate-co-ethyl acrylate), poly(methyl methacrylate-co-vinyl acetate), or a mixture of poly(methyl methacrylate-co-ethyl acrylate) and poly(methyl methacrylate-co-vinyl acetate). 
     
     
       20. The activator of claim 12 wherein the coating is a synthetic rubber. 
     
     
       21. The activator of claim 12 wherein the coating is a wax selected from the group consisting of paraffin wax, bees wax, branched-chain hydrocarbons, a mixture of esters of higher fatty acids, higher fatty alcohols free higher acids, free higher alcohols, and saturated hydrocarbons, and mixtures of any of the foregoing. 
     
     
       22. The activator of claim 12 wherein the plurality of salt crystals further includes sodium acetate trihydrate, a eutectic combination of sodium thiosulfate pentahydrate and sodium acetate trihydrate, or both. 
     
     
       23. A process for making an activator for initiating solidification of a supercooled salt solution, the process comprising the steps of: forming a shaped solid comprising a plurality of salt crystals selected from the group consisting of sodium thiosulfate pentahydrate, sodium acetate trihydrate, and a eutectic combination of sodium thiosulfate pentahydrate and sodium acetate trihydrate by pressing to provide a shaped solid fracturable by hand to produce at least two pieces; and   coating the solid completely with a synthetic rubber coating or a wax coating that is impervious to a supercooled salt solution to which the activator is added, the coating fracturing upon fracturing of the shaped solid.   
     
     
       24. The process of claim 23 wherein in the coating step, a coating solution comprising a coating solute and a solvent is applied onto the shaped solid. 
     
     
       25. The process of claim 24 wherein the coating step further includes the step of allowing the solvent to evaporate. 
     
     
       26. The process of claim 23 wherein the coating step includes the step of applying the coating as a sheet and sealing the sheet around the shaped solid. 
     
     
       27. The process of claim 23 wherein the coating step includes the step of applying the coating as a sleeve and sealing the sleeve around the shaped solid. 
     
     
       28. The process of claim 23 further comprising the step of scoring the shaped solid to facilitate featuring the shaped solid into two or more pieces. 
     
     
       29. The process of claim 23 wherein in the forming step the salt crystals are pressed into a shaped solid having a shape selected form the group consisting of cylinder, ovoid, sphere, parallelepiped, pyramid, cone, and polyhedron. 
     
     
       30. The process of claim 23 wherein the coating is poly(methyl methacrylate-co-ethyl acrylate), poly(methyl methacrylate-co-vinyl acetate), or a mixture of poly(methyl methacrylate-co-ethyl acrylate) and poly(methyl methacrylate-co-vinyl acetate). 
     
     
       31. The process of claim 23 wherein the coating is a synthetic rubber. 
     
     
       32. The process of claim 23 wherein the coating is a wax selected from the group consisting of paraffin wax, bees wax, branched-chain hydrocarbons, a mixture of esters of higher fatty acids, higher fatty alcohols, free higher acids, free higher alcohols, and saturated hydrocarbons, and mixtures of any of the foregoing.